NCERT CLASS 10TH CHAPTER: CONTROL AND COORDINATION REVIEW AND NOTES

NCERT CLASS 10^TH CHAPTER: CONTROL AND COORDINATION  REVIEW AND NOTES 

CONTROL- power of restrain and regulation by which something can be started, stopped down, expedited or stopped

COORDINATION- orderly or harmonious working of different but interrelated parts, to perform one or more activities very smoothly

Coordination in plants-

PLANTS MOVEMENTS-

Mainly divide into two types

1.      Tropic movement- directional movement- direction of movement is determined by the direction of stimulus

a.       Photo-tropism

                                                  i.      Positive – stem

                                                ii.      Negative- root

b.      Geo-tropism

                                                  i.      Positive- root

                                                ii.      Negative- stem

c.       Chemo-tropism- movement of pollen tube and fungal hyphae

d.      Hydro-tropism- root of seedling

2.      Nastic movements- non-directional movements- movement of plant parts in response to an external stimulus in which the direction of response is not determined by the direction of stimulus

1.      Nyctinasty- sleep movements- due to day and night e.g. daily movement of leaves, flowers, stomata

2.      Thigmotropism- haptotropism, in response to touch- tendrils of insectivores’ plants e.g. tendrils of Cuscuta

3.      Seismonasty- turgor changes occur in thin-walled cells of pulvinus e.g. Mimosa pudica

4.      Photonasty- Dandelion flower

Phytohormones-

Phytohormones are organic substance produced naturally in plants- controlling growth and other functions at a site remote its place and production and active in minute amounts

Phytohormones mainly are two types- these are

1.      Plant growth regulators- auxins, gibberellins, and cytokinin’s

2.      Plant growth inhibitors- ethylene, and ABA-abscisic acid

I.            Auxins- weakly acidic, growth promoting, produced from the root and shoot tips of plant body- migrate to the one of their action

Functions- promote cell division, cell elongation, root formation, respiration, protein synthesis, apical dominance and enhance physiological and reproductive activities.

II.            Gibberellins- weakly acidic, tetracyclic. Named after the fungus – Gibberellin fujikuroi

Functions- stimulate cell division, stem elongation, seed germination, flowering and increase in size of fruits, break dormancy of buds and seeds, more potent than auxins in parthenocarpy.

III.            Cytokinin’s- mildly alkaline, produced in dividing cells throughout the plant. In mature plants – produce in root tips and transported by stem

Functions- promote cytokinesis- cell division, causes differentiation of cells and tissue, cell elongation, break dormancy, regulate nutrient transport, enhance chloroplast development, increase resistance to disease.

IV.            Ethylene- gaseous hormone- produced in higher plants in stress, inhibits longitudinal growth, retards flowering, causes faster abscission of leaves and flowers and induce fruit ripening. Found in large quantities in ripening fruits- helps to overcome dormancy

V.            Abscisic acid (ABA)- (stress hormones)- growth inhibitor. Counteracts auxin, gibberellins and cytokinin’s.

Functions- Cause faster abscission of leaves and flowers, induce dormancy of seed, tubers and bulbs